X-ray is generally defined as an electromagnetic wave having a short wavelength corresponding to wavelengths of 0.01 nm to 10 nm, and an X-ray photographing is referred to as a radiography that transparently displays an inside of a photographing target by the high penetrable X-rays.
As well known, the X-ray involves an attenuation phenomenon depending on a material, a density, and a thickness of an object such as Compton scattering, a photoelectric effect, or the like during a process in which the X-ray penetrates through the object. Therefore, the X-ray photographing projects and displays the inside of the photographing target on a plane based on an amount of attenuation of the X-ray accumulated during the process in which the X-ray penetrates through the photographing target, and to this end, a dedicated X-ray system is used.
Recently, an X-ray imaging technology has rapidly evolved to a digital X-ray imaging technology having various advantages such as relatively high resolution, a wide dynamic region, an easy generation of an electrical signal, simple data process and storage, and the like, instead of a conventional analog scheme using a film while being grafted to a semiconductor field. A digital based imaging technology meets the clinical and environmental requirements of an early diagnosis of diseases based on excellent diagnostic ability of a digital image.
Therefore, “digital mammography”, which is a breast dedicated X-ray photographing technology capable of detecting a lesion and a micro-calcification for detection and early diagnosis of a breast cancer by expressing an internal structure of the breast in a high resolution image utilizing unique contrast ability of biological tissues of the X-ray has been proposed. The above-mentioned digital mammography has rapidly propagated due to unique characteristics such as an image expansion, a reduction in the number of photographs, an increase in resolution, and minimization of exposure through an adjustment of brightness and contrast ratio, together with various advantages of the digital X-ray imaging technology.
A general mammography device includes a column of a column shape which is perpendicular to a bottom; a C-arm that generally shows a C letter or a shape similar to the C letter at both end portions which are bent in arc shapes facing each other in a state in which a middle portion is connected so as to be elevatable and rotatable along the column; an X-ray generator mounted in one end portion of the C-arm to irradiate X-ray toward the other end portion facing one end portion; a detector mounted in the other end portion of the C-arm to face the X-ray generator; and a pressure pad performing a straight-line reciprocating motion between the X-ray generator and the detector along an internal surface of the C-arm.
In the mammography device as described above, when a patient enters a photographing position, the C-arm is elevated and rotated along the column to adjust a height and an angle so that the breast of the patient is placed at a target position on the detector, and when the pressure pad is moved in a direction of the detector to pressurize the breast, the X-ray is irradiated from the X-ray generator and is received at the detector. The detector generates an electrical signal for each position which is proportional to an incident amount of X-ray, and when the electrical signal and position information are read and are processed by an image processing algorithm, an X-ray image of the breast for the corresponding angle may be obtained. If necessary, the above-mentioned process may be repeated while the X-ray generator and the detector are rotated to face each other while having the breast therebetween, and as a result, the mammography device may obtain high resolution images for the breast of the patient at various angles.
In the general mammography device showing the above-mentioned photographing principle, a key driving mechanism for minimizing inconvenience of the patient and obtaining a high quality X-ray image is a pressure operation of the pressure pad. That is, since the pressure pad directly applies pressure to the breast during the X-ray photographing, it is directly related to pain or inconvenience which is felt by the patient. According to the related art, when the pressure pad pressurizes the breast placed on an inspection plate, more pressure than necessary may be applied, and as a result, there is a possibility that the patient undergoes more pain than necessary. Particularly, since sizes, densities, and the like of the breast of the patients are different from each other, suitable pressure should be applied accordingly, but there is a problem that the suitable pressure is not accurately and reliably controlled. An improvement method capable of increasing reliability for the pressure operation of the pressure pad and precisely and accurately controlling the pressure operation is required.